In order to further evaluate this PrEP strategy, we plan to measure the amount of maraviroc in the blood and genital tract of HIV-negative healthy female volunteers before, during, and after they are given maraviroc dosed either in the standard (twice a day) or reduced (once a day) dose for 7 days compared with women who are not given maraviroc. We will also study immune cells from the blood and genital tract from these women to see if maravoric has an effect on these cells that would prevent them from becoming infected with HIV.